Plasma processing apparatus and the upper electrode unit

ABSTRACT

In a plasma processing apparatus that executes plasma processing on a semiconductor wafer placed inside a processing chamber by generating plasma with a processing gas supplied through a gas supply hole at an upper electrode (shower head) disposed inside the processing chamber, an interchangeable insert member is inserted at a gas passing hole at a gas supply unit to prevent entry of charged particles in the plasma generated in the processing chamber into the gas supply unit. This structure makes it possible to fully prevent the entry of charged particles in the plasma generated inside the processing chamber into the gas supply unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application Ser. No.12/405,432, filed Mar. 17, 2009, now abandoned, of Tetsuji SATO forPLASMA PROCESSING APPARATUS AND THE UPPER ELECTRODE UNIT, which is adivisional of application Ser. No. 10/830,355, filed Apr. 23, 2004, nowabandoned, of Daisuke HAYASHI et al. for PLASMA PROCESSING APPARATUS,the entireties of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma processing apparatus, and morespecifically, it relates to a plasma processing apparatus that does notallow charged particles of plasma generated in a processing chamber toenter a gas supply unit.

2. Description of the Related Art

Plaza processing apparatuses in the known art include those that executeplasma processing such as etching on the work surface of a workpiece,e.g., a semiconductor wafer (hereafter simply referred to as a “wafer”)placed within a processing chamber by, for instance, supplying aprocessing gas from a gas supply unit into the processing chamber andgenerating plasma with the processing gas.

The gas supply unit in such a plasma processing apparatus is constitutedas a shower head having numerous gas supply holes through which theprocessing gas is supplied into the processing chamber. The plasmaprocessing apparatus may be, for instance, a plane parallel plasmaprocessing apparatus having a lower electrode disposed within theprocessing chamber, on which the workpiece is placed. The gas supplyunit is constituted of a shower head also functioning as an upperelectrode which is disposed at the ceiling of the processing chamber soas to face opposite the lower electrode.

The gas supply unit includes an electrode plate that constitutes thelower surface thereof, in which numerous gas supply holes are formed andan electrode support body supporting the electrode plate. Inside theelectrode support body, a buffer chamber is formed as a space locatedabove the electrode plate and communicating with a gas supply pipe, andthe buffer chamber also communicates with the gas supply holes at theelectrode plate. The gas flowing in through the gas supply pipe is firstsupplied into the buffer chamber and is then guided from the bufferchamber into the processing chamber via the gas supply holes at theelectrode plate.

However, charged particles such as electrons and ions in the plasmagenerated with the processing gases inside the processing chamber mayenter the buffer chamber through the gas supply holes at the gas supplyunit in the plasma processing apparatus. If charged particles in theplasma enter the gas supply unit (shower head), a glow discharge occursin the buffer chamber at the gas supply unit, giving rise to problemssuch as reaction products becoming adhered to the inner surfaces of thegas supply unit and the inner surfaces of the gas supply unit becomingcorroded.

These problems are addressed in, for instance, Japanese Patent Laid-openPublication No. 9-275093, which discloses a structure achieved bymounting a screw having a hole decentered from the central axis at eachgas outlet hole of the gas supply means so that there is no clearpassage from one opening end of the gas supply hole through the otheropening end to prevent entry of electrons and ions in the plasma intothe gas supply means. This technology was developed in order to minimizethe entry of charged particles through the mean free path based upon theconcept that the charged particles in the plasma are allowed to enterthe gas supply means since the thickness of the electrode plate (theheight of the gas supply holes) is approximately equal to the length ofthe mean free path of the charged particles in the plasma.

However, the charged particles in the plasma enter the gas supply meansnot only through the mean free path but also because of other factors.For instance, the potential (the ground potential) at the electrodesupport body constituting the upper wall of the buffer chamber in thegas supply unit may become lower than the potential (ground potential)at the electrode plate constituting the lower wall of the bufferchamber. In such an event, the charged particles in the plasma areallowed to readily enter the buffer chamber from the gas supply holes atthe electrode plate toward the electrode support body. In addition,while the gas supply unit normally maintains a field free state inside,the equipotential line will become skewed at an end of a gas supply holeand shifts into the gas supply hole if the gas supply hole is clear,thereby allowing a concentration of energy of the electrons and the likeand allowing the electrons and the like to readily enter the gas supplyhole.

For this reason, charged particles in the plasma cannot be fullyprevented from entering the gas supply means simply by mounting a screwhaving a hole decentered from the central axis at each gas outlet holeof the gas supply means as disclosed in Japanese Patent Laid-openPublication No. 9-275093. For instance, since high-frequency powercauses charged particles such as electrons to vibrate along a directionperpendicular to the equipotential line, the oscillating direction ofthe charged particles becomes tilted if the equipotential line becomesskewed and shifts into the end portion of the gas supply hole. In such acase, the entry of the charged particles cannot be fully preventedsimply by mounting a screw having a hole decentered from the centralaxis.

Furthermore, entry of the charged particles in the plasma is most likelyto occur when various conditions such as a specific gas supply holediameter, a specific gas type and a specific plasma density coincide.This leads to a concept that if the gas passage at the gas supply holecan be altered in correspondence to predetermined conditions, the entryof the charged particles in the plasma into the gas supply unit can beprevented more effectively.

Accordingly, an object of the present invention, which has beencompleted by addressing the problems discussed above, is to provide aplasma processing apparatus capable of fully preventing chargedparticles in the plaza generated inside the processing chamber fromentering the gas supply unit.

SUMMARY OF THE INVENTION

In order to achieve the object described above, in an aspect of thepresent invention, a plasma processing apparatus that executes plasmaprocessing on a workpiece placed inside a processing chamber bygenerating plasma with a processing gas supplied through gas supplyholes of gas supply unit disposed inside the processing chamber,characterized in that an interchangeable insert member, which preventscharged particles in the plasma generated inside the processing chamberfrom entering the gas supply unit, is mounted at each gas supply hole atthe gas supply unit, is provided.

The insert member may include a gas passage communicating between theentry side and the exit side of the gas supply hole, and the gas passagemay include a passage which extends along a direction perpendicular toor at an angle to a central axis of the gas supply hole so as toregulate the flow along the central axis.

Alternately, the insert member may include a gas passage formed, forinstance, as a spiral gas passage, which communicates between the entryside and the exit side of the gas supply hole while constantlyregulating the flow in the gas supply hole along the central axis. Sucha gas passage may be formed so that its section has a width (groovedepth) along the direction perpendicular to the central axis of the gassupply hole larger than the thickness of the passage along the centralaxis of the gas supply hole.

In addition, an insert member constituted of a specific material may beused in conjunction with a specific gas type used for the plasmaprocessing. Furthermore, the shape of the gas passage in the insertmember may be determined in correspondence to the density of the plasmagenerated in the processing chamber.

Even if charged particles such as electrons in the plasma enter throughthe gas supply hole the flow of the charged particles inside the gassupply hole is regulated along the central axis and the chargedparticles are thus caused to collide into the inner wall or the like ofthe insert member and lose energy before they reach the upper end of theinsert member in the plasma processing apparatus according to thepresent invention described above. In particular, even if theequipotential line becomes skewed at the end of the gas supply hole, theoscillating direction of the charged particles such as electrons becomestilted and, as a result, the charged particles enter the gas supplyhole, the movement of the charged particles along the central axis isregulated through the gas passage. Thus, the entry of the chargedparticles in the plasma into the gas supply unit can be prevented with ahigh degree of reliability. This, in turn, effectively prevents anyoccurrence of a glow discharge in the gas supply unit since no energy istransferred into the gas supply unit.

Moreover, since interchangeable insert members are used according to thepresent invention, optimal insert members can be mounted at the gassupply unit in correspondence to various conditions such as the specificgas type and the specific plasma density.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of the structure adopted in anetching apparatus in an embodiment of the present invention;

FIG. 2 is a schematic sectional view of the structure adopted in theupper electrode (shower head) in the embodiment;

FIG. 3 is a schematic a sectional view of the upper electrode which doesnot include the insert members achieved in the embodiment;

FIG. 4 presents a structural example that may be adopted in the insertmembers in the embodiment, with FIG. 4A showing an external view of aninsert member and FIG. 4B showing a sectional view of an insert member;

FIG. 5 presents another structural example that may be adopted in theinsert members in the embodiment, with FIG. 5A showing an external viewof an insert member and FIG. 5B showing a sectional view of an insertmember;

FIG. 6 is a perspective of another structural example that may beadopted in the insert members in the embodiment;

FIG. 7 presents sectional views of the insert member in FIG. 6, withFIG. 7A showing a sectional view of the insert member in FIG. 6 takenalong A-A and FIG. 7B showing a sectional view of the insert member inFIG. 6 taken along B-B;

FIG. 8 schematically illustrates the overall structure of another plasmaprocessing apparatus in which the present invention may be adopted;

FIG. 9 schematically illustrates the structure of an essential portionof the plasma processing apparatus in FIG. 8;

FIG. 10 schematically illustrates the structure of an essential portionof the plasma processing apparatus in FIG. 8;

FIG. 11 schematically illustrates the structure of an essential portionof the plasma processing apparatus in FIG. 8;

FIG. 12 is a schematic sectional view of the structure adopted inanother plasma processing apparatus in which the present invention maybe adopted;

FIG. 13 is a sectional view of the plasma processing apparatus in theembodiment shown in FIG. 12 with its upper electrode set at a processingposition;

FIG. 14 presents simplified views of the upper electrode unit achievedin the embodiment, with FIG. 14A showing the upper electrode unit withthe upper electrode set at a retracted position and FIG. 14B showing theupper electrode unit with the upper electrode set at the processingposition;

FIG. 15 shows the structure adopted in the means for drive control atthe upper electrode drive mechanism in the embodiment;

FIG. 16 is a block diagram of the upper electrode position controlexecuted by the CPU shown in FIG. 15;

FIG. 17 shows the structure adopted in the pneumatic circuit in theembodiment;

FIG. 18 illustrates the functions of the pneumatic circuit in theembodiment;

FIG. 19 illustrates the functions of the pneumatic circuit in theembodiment;

FIG. 20 shows the results of position control achieved by driving theupper electrode in the embodiment upward; and

FIG. 21 shows the results of position control achieved by driving theupper electrode in the embodiment downward.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed explanation of the preferred embodiments ofthe present invention, given in reference to the attached drawings. Itis to be noted that the same reference numerals are assigned tocomponents having substantially identical functions and structuralfeatures in the specification and drawings to preclude the necessity fora repeated explanation thereof.

(Plasma Processing Apparatus Achieved in an Embodiment of the PresentInvention)

The structure adopted in the plasma processing apparatus achieved in anembodiment of the present invention is now explained in reference toFIG. 1. FIG. 1 is a sectional view of the structure of a plasmaprocessing apparatus achieved in the embodiment. A plasma processingapparatus 100, which is an RIE plasma etching apparatus, includes acylindrical processing chamber (chamber) 110 constituted of a metal suchas aluminum or stainless steel. The processing chamber 110 is groundedfor protection.

Inside the processing chamber 110, a disk-shaped lower electrode(susceptor) 112, on which a workpiece such as a semiconductor wafer(hereafter simply referred to as a wafer) is placed, is disposed. Thelower electrode 112 constituted of, for instance, aluminum is supportedby a barrel-shaped supporting unit 116 extending upward perpendicular tothe bottom of the processing chamber 110 via an insulating barrel-shapedholding unit 114. At the upper surface of the barrel-shaped holding unit114, a focus ring 118 constituted of, for instance, quartz, whichencircles the upper surface of the lower electrode 112, is disposed.

An evacuating passage 120 is formed between the side wall of theprocessing chamber 110 and the barrel-shaped supporting unit 116. Anannular baffle plate 122 is mounted either at the entrance to or in themiddle of the evacuating passage 120, and an evacuation port 124 isprovided at the bottom of the evacuating passage 120. An evacuationdevice 128 is connected to the evacuation port 124 via an evacuationpipe 126. The evacuation device 128, which includes a vacuum pump (notshown), is capable of reducing the pressure in the processing spacewithin the processing chamber 110 to a predetermined degree of vacuum. Agate valve 130, which opens/closes the delivery bay through which thewafer W is carried in/out is mounted at the side wall of the processingchamber 110.

A high-frequency source 132 for plasma generation and also for RIE iselectrically connected to the lower electrode 112 via a matcher 134 anda power supply rod 136. High-frequency power with a predeterminedfrequency, e.g., 60 MHz, is applied to the lower electrode 112 from thehigh-frequency source 132. In addition, at the ceiling of the processingchamber 110, a shower head (hereafter referred an “upper electrode”) 138to be detailed later, which is used to supply a processing gas and alsofunctions as an upper electrode, is disposed at a position facingopposite the lower electrode 112. The potential at the upper electrode138 is set to ground level. Thus, the high-frequency voltage from thehigh-frequency source 132 is capacitatively applied between the lowerelectrode 112 and the upper electrode 138.

An electrostatic chuck 140 that holds the wafer W by electrostaticallyattracting the wafer W is provided at the upper surface of the lowerelectrode 112. The electrostatic chuck 140 is constituted by enclosingan electrode 140 a formed from a conductive film between a pair ofinsulating films 140 b and 140 c. A DC source 142 is electricallyconnected with the electrode 140 a via a switch 143. As a DC voltage issupplied from the DC source 142, the wafer W is attracted and held ontothe electrostatic chuck 140 with the resulting coulomb force.

A coolant chamber 144, which may extend along, for instance, thecircumferential direction is provided inside the lower electrode 112. Acoolant such as cooling water sustaining a predetermined temperature andsupplied from a chiller unit 146 via pipings 148 and 150 circulatesthrough the coolant chamber 144. The temperature of the wafer W on thelower electrode 112 can be controlled in correspondence to thetemperature of the coolant. In addition, a heat transfer gas such as anHe gas is supplied from a heat transfer gas supply unit 152 via a gassupply line 154 to the space between the upper surface of theelectrostatic chuck 140 and the back surface of the wafer W.

As FIG. 2 also shows, the upper electrode (shower head) 138 includes anelectrode plate 156 located on the lower side, at which numerous gaspassing holes 156 a are formed, an electrode support body 158 whichdetachably supports the electrode plate 156 and an intermediate member157 disposed on top of the electrode plate 156 and having gascommunicating holes 157 a each communicating with one of the gas passingholes 156 a at the electrode plate 156. The gas supply holes at the gassupply unit according to the present invention are each constituted witha gas passing hole 156 a and the corresponding gas communicating hole157 a described above. Inside the electrode support body 158, a bufferchamber 160 is formed and a gas supply piping 164 extending from aprocessing gas supply unit 162 is connected to a gas supply port 160 aat the buffer chamber 160.

The processing chamber 110 is enclosed by a dipole ring magnet 166. Thedipole ring magnet 166 is constituted with a pair of annular or coaxialmagnets disposed at an upper position and a lower position over adistance from each other in the embodiment. The magnets constituting thedipole ring magnet 166 are each achieved by housing a plurality ofanisotropic segment pole magnets in a ring-shaped casing formed of amagnetic material so that they form uniform horizontal magnetic fieldsthat are oriented in a single direction as a whole inside the processingchamber 110. As the processing gas is supplied into the processingchamber 110, a magnetron discharge is caused by an RF electric fieldalong the vertical direction attributable to the high-frequency source132 and the horizontal magnetic field attributable to the dipole ringmagnet 166 in the space between the upper electrode 138 and the lowerelectrode 112 in the processing chamber 110 and, as a result,high-density plasma is generated near the surface of the lower electrode112.

The plasma processing apparatus includes a control unit 168 thatcontrols the individual units in the apparatus. The control unit 168controls the operations of, for instance, the evacuation device 128, thehigh-frequency source 132, the switch 143 for the electrostatic chuck,the chiller unit 146, the heat transfer gas supply unit 152 and theprocessing gas supply unit 162. The control unit 168 may be connected toa host computer within the factory (not shown) to enable control fromthe host computer.

When executing, for instance, an etching process with the plasmaprocessing apparatus 100 structured as described above, the gate valve130 is first set in an open state to allow the wafer W, i.e., theworkpiece, to be carried into the processing chamber 110 and placed onthe lower electrode 112. At this time, a DC voltage from the DC source142 is applied to the electrode 140 a of the electrostatic chuck 140 toelectrostatically attract the wafer W onto the lower electrode 112.Then, a specific type of processing gas such as NH3 is supplied from theprocessing gas supply unit 162 into the processing chamber 110 at apredetermined flow rate and a predetermined flow rate ratio, and thepressure inside the processing chamber 110 is set to a predeterminedvalue via the evacuation device 128. In addition, high-frequency powerat a specific frequency is applied from the high-frequency source 132 tothe lower electrode 112 at a predetermined power level. The processinggas supplied into the processing chamber 110 via the upper electrode 138as described above is raised to plasma between the two electrodes 112and 138 through a high-frequency discharge and the work surface of thewafer W is etched with radicals and ions occurring in the plasma.

By applying high-frequency power at a frequency higher than that in therelated art, e.g., 50 MHz or higher, to the lower electrode 112, ahigher density can be achieved for the plasma in a more desirable stateof dissociation and high density plasma can be formed at a lowerpressure.

Next, the upper electrode (shower head) 138 representing an example thatmay be adopted in the gas supply unit in the embodiment is explained infurther detail in reference to drawings. FIG. 2 is a sectional view ofthe structure adopted in the upper electrode in the embodiment, whereasFIG. 3 presents another example of an upper electrode provided forcomparison with the upper electrode in the embodiment.

As shown in FIG. 2, insert members 200 are inserted at gas passing holes156 a constituting part of the gas supply holes, which are located atthe electrode plate 156 in the upper electrode 138 in the embodiment.The insert members 200, which can be attached to and detached from theelectrode plate 156 freely, can be replaced by insert members 200 withany of various structures featuring gas passages formed in differentshapes and constituted of different materials, in correspondence tovarious conditions such as the gas type and the plasma density level.The insert members 200 are used to prevent charged particles such aselectrons and ions in the plasma generated within the processing chamber110 from entering the upper electrode through the gas passing holes 156a. The insert members 200 each include a gas passage 212 through whichthe processing gas flows. The gas passage 212 is formed so that entry ofcharged particles in the plasma is disallowed while the processing gasis allowed to flow through it. It is to be noted that the structure ofthe insert members 200 is to be described in detail later.

If the insert members 200 are not inserted at the gas passing holes 156a of the upper electrode 138 as shown in FIG. 3, charged particles inthe plasma may enter the upper electrode 138 through the gas passingholes 156 a at the electrode plate 156. Electrons, which moveparticularly fast among charged particles, can enter the gas supply unitwith ease. If charged particles in the plasma enter the upper electrode138, a glow discharge occurs in the buffer chamber 160 inside the upperelectrode 138, which results in reaction products becoming adhered tothe inner surfaces at the upper electrode 138 and corrosion inside theupper electrode.

In addition, while the charged particles in the plasma are allowed toenter the upper electrode 138 when the length of the mean free path ofthe charged particles in the plasma is substantially equal to or greaterthan the thickness of the electrode plate 156 (the height of the gassupply holes), entry of charged particles may be attributed to thefollowing causes as well. For instance, the potential (the groundpotential) at the electrode support body 158 constituting the upper wallof the buffer chamber 160 in the upper electrode 138 may become lowerthan the potential (the ground potential) at the electrode plate 156,which is in electrical contact with the intermediate member 157constituting a lower wall of the buffer chamber 160. In such an event,charged particles in the plasma are allowed to enter the buffer chamber160 with greater ease from the gas passing holes 156 a at the electrodeplate 156 and flow toward the electrode support body 158.

In addition, while the upper electrode 138 normally maintains a fieldfree state inside, the equipotential line will become skewed at the endsof the gas supply holes (each constituted with a gas passing hole 156 aand the corresponding gas communicating hole 157 a) and shifts into anyclear gas supply hole, thereby allowing a concentration of the energy ofthe electrons and the like in the gas supply hole. Namely, when chargedparticles such as electrons are caused to oscillate by high-frequencypower, they oscillate along a direction perpendicular to theequipotential line and thus, if the equipotential line becomes skewedand shifts into the end of a gas supply hole, the oscillating directionof the charged particles, too, becomes tilted, which causes the energyof the charged particles such as electrons to readily concentrate at theend portion of the gas supply hole. As a result, the charged particlessuch as electrons are allowed to enter the gas supply holes with ease.Under these circumstances, the charged particles are more likely toenter the buffer chamber 160 while holding a high level of energy.

Such entry of charged particles from the plasma can be prevented byforming a passage extending along a direction perpendicular to or at anangle to the central axis of each gas supply hole so as to regulate theflow along the central axis. The entry of the charged particles in theplasma can be prevented more effectively as the length of the passageextending along the direction perpendicular to or at an angle to thecentral axis increases, since the charged particles in the plasma alongthe vertical direction will more readily collide with the wall or thelike defining the gas passage as the length of the passage extendingalong the direction perpendicular to or at an angle to the central axisincreases and thus, the energy level of the charged particles in theplasma can be kept low. The presence of such a passage at each gassupply hole prevents the charged particles in the plasma from advancingto the buffer chamber 160 at the upper electrode 138.

Furthermore, the charged particles in the plasma are likely to enter theupper electrode 138 most readily when various conditions such as aspecific gas supply hole diameter, a specific gas type and a specificsplasma density level coincide. This leads to a concept that if the gaspassage at the gas supply hole can be altered in correspondence topredetermined conditions, the entry of the charged particles from theplasma into the upper electrode 138 can be prevented more effectively.

Based upon this concept, an insert member 200 is inserted at each of thegas supply holes at the upper electrode 138 and the part of the gaspassage formed at the insert member, which extends vertically or at anangle is made to range over a sufficient length, according to thepresent invention. In addition, insert members 200 can be replaced witha different type of insert members in conformance to various conditionssuch as the gas type and the plasma density so as to alter the passagethrough the gas supply hole to adjust to specific conditions.

Next, structural examples that may be adopted in the insert members 200inserted at the gas passing holes 156 a constituting part of the gassupply holes at the upper electrode 138 as described above are explainedin reference to drawings. FIG. 4 presents a structural example that maybe adopted in the insert members mounted at the gas supply holes of theupper electrode. FIG. 4A presents an external view of an insert member,whereas FIG. 4B presents a sectional view of the insert member mountedat a gas passing hole 156 a.

As shown in FIGS. 2 and 4B, the gas passing holes 156 a formed at theelectrode plate 156 of the upper electrode 138 are each constituted witha hole 156 b formed on the side toward the intermediate member 157 and ahole 156 c which communicates with the hole 156 b and has a diametersmaller than that of the hole 156 b. The insert members 200 are insertedat the hole 156 b which constitute part of the gas passing holes 156 aand are formed on the side toward the intermediate member 157.

The insert members according to the present invention each include a gaspassage formed to extend along a direction perpendicular to or at anangle to the central axis of the gas supply hole so as to regulate theflow along the central axis. For instance, a gas passage 202 at theinsert member 200 in FIG. 4 is formed in a spiral shape so as tocommunicate between the upper end and the lower end of the insert member200 while constantly regulating the flow along the central axis at thegas passing hole 156 a. In more specific terms, such a gas passage maybe achieved by forming a spiral groove at the external circumferentialsurface of the insert member 200, as shown in FIG. 4A, for instance. Thegas passage 202 is formed by this spiral groove and the inner wall ofthe gas passing hole 156 a as the insert member 200 is inserted at thegas passing hole 156 a. It is to be noted that although not shown, thegas passage may instead be formed in a zigzag pattern at the insertmember.

In addition, as shown in FIG. 4B, the gas passage 202 may be formed sothat its section has a width (groove depth) along a direction extendingperpendicular to the central axis of the gas passing hole, which islarger than the thickness of the gas passing hole 156 a along thecentral axis. As the number of turns of the spiral gas passage 202increases, the entry of charged particles can be prevented with greatereffectiveness. However, as the number of turns of the spiral gas passage202 increases, the gas passage becomes narrower, resulting in a loweredflow rate of the processing gas. Accordingly, the number of turns thatthe spiral gas passage 202 makes should be determined so as to strike anoptimal balance between the desired level of charged particle entryprevention and the desired processing gas flow rate. For instance, it isdesirable to form the spiral gas passage so that it makes 1.5 turns ormore at the external side surface of the insert member 200.

When such insert members 200 are inserted at the individual gas passingholes 156 a, the gas passages 202 of the insert members 200 regulate theflow along the central axes of the individual gas passing holes 156 a atall times and thus, any charged particles in the plasma that may enterthrough the gas passing holes 156 a are bound to collide into the innerwalls or the like of the insert members 200 and lose their energy beforethey reach the upper ends of the insert members 200.

Furthermore, even if the equipotential line becomes skewed at the end ofa gas passing hole 156 a and the direction along which charged particlessuch as electrons oscillate becomes tilted as a result to allow thecharged particles to enter through the gas passing hole 156 a, the flowalong the central axis of the gas passing hole 156 a is regulated by thegas passage 202 at all times. Thus, the charged particles collide intothe inner wall or the like of the insert member 200 and their energybecomes dissipated before they reach the upper end of the insert member200.

Consequently, the charged particles in the plasma are prevented fromentering the buffer chamber 160 inside the upper electrode 138 with ahigh degree of effectiveness. With no energy transferred into the bufferchamber 160, it is ensured that a glow discharge does not occur withinthe buffer chamber 160.

In addition, since the gas passage 202 of the insert member 200 isformed so that its thickness along the central axis of the gas passinghole 156 a is smaller than its width (groove depth) along the directionperpendicular to the central axis, as shown in FIG. 4B. The space insidethe gas passing hole 156 a along the axial direction can be narrowed tocause charged particles such as electrons to readily collide into thewall and the like of the insert member 200 and to lose energy quickly.Furthermore, as the flow rate of the processing gas can be increased,the occurrence of a glow discharge inside the upper electrode 138 can beprevented without having to greatly alter the gas outlet characteristicsof the upper electrode (shower head) 138.

It is to be noted that the insert members according to the presentinvention may each be detachably mounted through the entire length ofthe gas passing hole 156 a at the electrode plate 156, as in the case ofan insert member 210 shown in FIG. 5. FIG. 5A presents an external viewof the insert member 210, whereas FIG. 5B is a sectional view of theinsert member 210 mounted at the gas passing hole 156 a. A gas passage212 of this insert member 210 may be formed over the entire insertmember 210, as shown in FIG. 5A, for instance.

In another specific example of the insert members according to thepresent invention, the gas passage formed to regulate the flow along thecentral axis of the gas supply hole and extends along the directionperpendicular to or at an angle to the central axis may be present alongboth the diameter and the circumference of the insert member. Morespecifically, it may be provided as an insert member 230 shown in FIGS.6 and 7. FIG. 6 is a perspective showing the structure adopted in theinsert member 220, whereas FIG. 7A and FIG. 7B are both sectional viewstaken along A-A and B-B in FIG. 6 respectively.

The insert member 220 is detachably inserted at the hole 156 b in thegas passing hole 156 a at the electrode plate 156, as is the insertmember 200 shown in FIG. 4. As shown in FIGS. 6 and 7, the insert member220 has an overall shape of a substantially circular column with acircumferential groove 224 formed at a substantially middle portion ofthe outer side surface.

At a lower position relative to the circumferential groove 224 of theinsert member 220, an axial hole 226 is formed along the axis of the gaspassing hole 156 a and a diameter-direction hole 228 is formed along thediameter of the gas passing hole 156 a to communicate with the upper endof the axial hole 226, as shown in FIG. 7A. The diameter-direction hole228 is in communication with the circumferential groove 224. Thediameter-direction hole 228 and the circumferential groove 224 togetherform a passage extending perpendicular to or at an angle to the centralaxis of the gas supply hole.

As shown in FIG. 7B, at a position upward relative to thecircumferential groove 224 of the insert member 220, axial grooves 229are formed perpendicular to the direction along which thediameter-direction hole 228 is formed so as to cut through to the upperend of the insert member 220. The lower ends of the axial grooves 229are in communication with the circumferential groove 224.

As the insert member 220 is inserted at the gas passing hole 156 a, apassage is formed by the individual grooves and the inner wall of thegas passing hole 156 a. A gas passage 222 of the insert member 220adopting the structure described above extends upward from its lower endalong the axial direction through the axial hole 226, passes along thediameter through the diameter-direction hole 228 from the upper end ofthe axial hole 226, makes a 90° turn along the circumferential groove224 and then extends upward through the axial grooves 229 to the upperend of the gas passage 222.

By inserting this insert member 220 at each gas passing hole 156 a, itcan be ensured that even if charged particles in the plasma enter thegas passing hole 156 a, they cannot reach the axial grooves 229 withoutfirst advancing along the diameter through the diameter-direction hole228 and then making a 90° turn at the circumferential groove 224. Sincethe flow in the gas passing hole 156 a along its central axis isregulated with the passage extending both along the diameter and alongthe circumference in this manner, the charged particles are bound tocollide into the inner wall or the like of the insert member 220 andlose energy before they reach the upper end of the insert member 220.

In addition, even if the equipotential line becomes skewed at the end ofa gas passing hole 156 a causing a tilt in the direction along whichcharged particles such as electrons oscillate and the charged particlesare allowed to enter the gas passing hole 156 a, the flow in the gaspassing hole 156 a along the central axis is regulated by the gaspassage 222 at all times and thus, charged particles are bound tocollide into the inner wall or the like of the insert member 220 to loseenergy before they reach the upper end of the insert member 220.

Such insert members 220, too, make it possible to effectively prevententry of charged particles in the plasma into the buffer chamber 160 atthe upper electrode 138. As a result, no energy is transferred into thebuffer chamber 160 and the occurrence of a glow discharge inside thebuffer chamber 160 can be prevented with a high degree of reliability.

It is to be noted that the dimensions of the section of the gas passage222 at the insert member 220, too, should be determined so as to strikean optimal balance between the desired level of charged particle entryprevention and the desired processing gas flow rate. More specifically,if the diameter of the gas passing hole 156 a is approximately 4 mm to 5mm, it is desirable to set the height of the gas passing hole 156 aalong the axial direction over the diameter-direction hole 228 and thecircumferential groove 224 in the gas passage 222 to 0.5 mm to 1.5 mm.

Next, materials that may be used to constitute the insert membersaccording to the present invention, are explained. The insert members200, 210 and 220 described above may be constituted of a fluororesinsuch as Teflon (registered trademark), a tetrafluoroethylene resin(PTFE), a chlorine trifluoroethylene resin (PCTFE), atetrafluoroethylene parfluoroalkylvynylether copolymer resin (PFA), atetrafluoroethylene-hexafluoride propylene copolymer resin (PFE) or afluorovinyllidene resin (PVDF) instead of quartz. These materials aredesirable since they have low dielectric constants, achieve a high levelof voltage withstanding performance against AC voltages and can beprocessed with ease, which makes it possible to minimize productioncosts. Alternatively, the insert members may be constituted of a porousceramic instead of a resin. Furthermore, the insert members 200 achievedin the embodiment, which are used in the field free upper electrode 138,may instead be constituted of metal, e.g., aluminum, instead of resin.

The insert members mounted at the gas supply holes in the upperelectrode 138 in the embodiment are interchangeable. Accordingly, theoptimal type of insert members should be selected in correspondence tovarious conditions including the gas type and the plasma density to beinserted at the gas supply holes in the upper electrode 138. By usingthe optimal insert members, it is possible to fully prevent chargedparticles in the plasma generated in the processing chamber 110 fromentering the upper electrode 138, which constitutes the gas supply unit.

More specifically, insert members constituted of different materials maybe mounted in correspondence to different types of processing gases. Forinstance, insert members constituted of polyimide may be used inconjunction with a CF gas, and insert members constituted of PTFE with ahigh level of corruption resistance may be used in conjunction with acorrosive gas such as a NH3 gas, a HBR gas or a C12 gas.

In addition, insert members formed in different shapes may be mounted incorrespondence to different density levels of the plasma generatedinside the processing chamber 110. For instance, as the plasma densityrises, it becomes necessary to more rigorously ensure that chargedparticles in the plasma cannot enter the upper electrode readily and,accordingly, the insert members 200 or 210 having the spiral gaspassages 202 or 212 as shown in FIG. 4 or FIG. 5 should be used, whereasif the plasma density is low, the insert members 220 having the gaspassages 222 structured as shown in FIGS. 6 and 7 formed therein aregood enough.

As explained in detail above, the present invention provides a plasmaprocessing apparatus with which it is impossible to fully preventcharged particles in plasma generated inside the processing chamber fromentering the gas supply unit.

While the invention has been particularly shown and described withrespect to a preferred embodiment thereof by referring to the attacheddrawings, the present invention is not limited to this example and itwill be understood by those skilled in the art that various changes inform and detail may be made therein without departing from the spirit,scope and teaching of the invention.

For instance, while high-frequency power is applied to the lowerelectrode 112 alone and the upper electrode 138 is grounded in theexplanation given above on the plasma processing apparatus 100 achievedin the embodiment, the present invention may also be adopted in a plasmaprocessing apparatus in which high-frequency power is also applied tothe upper electrode 138 as well as to the lower electrode 112. In such acase, too, a glow discharge inside the upper electrode 138 can beprevented as effectively as in the embodiment.

In addition, the present invention may be adopted in a plasma processingapparatus other than a plane parallel plasma etching apparatus, such asa helicon wave plasma etching apparatus or an inductively coupled plasmaetching apparatus. In more specific terms, the present invention may beadopted in plasma processing apparatuses such as those explained inreference to FIGS. 8 to 11 and FIGS. 12 through 21.

(Another Example of Plasma Processing Apparatus in Which the PresentInvention May Be Adopted)

Next, another example of a plasma processing apparatus in which thepresent invention may be adopted is explained in reference to drawings.The plasma processing apparatus in this example is employed to executespecific types of plasma processing such as etching and film formationprocessing on work substrates, e.g., semiconductor wafers or glasssubstrates for liquid crystal display devices, by using plasma.

It is an established practice in the area of semiconductor deviceproduction to process a work substrate such as a semiconductor wafer ora glass substrate for a liquid crystal display device in a desiredmanner by employing a plasma processing apparatus that executes, forinstance, etching processing or film formation processing on the worksubstrate with plasma generated inside a vacuum chamber and applied ontothe work substrate.

In the plasma processing apparatus which may be a so-called planeparallel plasma processing apparatus, a stage on which the semiconductorwafer or the like is placed is provided inside the vacuum chamber, ashower head is provided at the ceiling of the vacuum chamber so as toface opposite the stage and a pair of plain parallel electrodes areconstituted with the stage and the shower head.

A specific type of processing gas is supplied from the shower head intothe vacuum chamber and at the same time, the vacuum chamber is evacuatedthrough its bottom so as to fill the vacuum chamber with a processinggas atmosphere achieving a predetermined degree of vacuum. In thisstate, high-frequency power with a predetermined frequency is suppliedbetween the stage and the shower head, thereby generating plasma withthe processing gas, and as the plasma is applied to the semiconductorwafer, the semiconductor wafer is processed, e.g., etched.

The plasma processing apparatus in the related art as described aboveinclude those having an evacuation ring formed as an annular platesurrounding the stage with numerous permeating hole or slit-shapedevacuating passages formed therein to achieve an even flow of theprocessing gas around the semiconductor wafer by uniformly evacuatingthe atmosphere around the stage and to prevent a plasma leak from theprocessing space (see, for instance, Japanese Utility Model PublicationNo. 5-8937 (FIGS. 1 through 3)).

While the evacuation ring has a function of preventing a plasma leakfrom the processing space within the vacuum chamber, as described above,it is necessary to ensure that electrons are not allowed to pass throughthe evacuating passages readily by reducing the opening area of theevacuating passages or increasing the length of the evacuating passagesin the evacuation ring in order to further improve the plasma leakpreventing effect. It is to be noted that if a plasma leak occurs, theplasma becomes unstable and it becomes difficult to execute a specifictype of plasma processing on the semiconductor wafer or the like. Forthis reason, the likelihood of a plasma leak needs to be minimized.

However, if the function of the evacuation ring for preventing plasmaleak is improved as described above, it becomes more difficult toachieve a sufficient level of conductance of the gas. This gives rise toa problem in that with the evacuation performance becoming poor, theprocesses that can be executed become limited. If, on the other hand,priority is given to high evacuation performance in order to avoid theproblem discussed above, it becomes necessary to use a largehigh-performance vacuum pump to result in an increase in the apparatusproduction costs.

As described above, if the function of the evaluation ring forpreventing a plasma leak is improved, the conductance of the gas becomespoor, and it is difficult to satisfy both the requirements for theplasma leak preventing function and the sufficient level of conductanceof the gas in the plasma processing apparatus in the related art. Thisleads to problems in that a desired type of plasma processing cannot beexecuted due to the occurrence of a plasma leak and in that theprocesses which can be executed become limited due to poor conductanceof the gas and the like.

Accordingly, an object of the present invention, which has beencompleted by addressing the problems discussed above, is to provide aplasma processing apparatus having a high level of gas conductancecapacity to enable a wide range of processes without increasing theproduction costs and also having an effective plasma leak preventingfunction to allow plasma processing to be executed in a desirable mannerwith stable plasma.

In order to achieve the object described above, in, an aspect of thepresent invention, a plasma processing apparatus comprising a vacuumchamber in which a work substrate is placed, a stage disposed within thevacuum chamber on which the work substrate is placed, a plasmagenerating mechanism that generates plasma within the vacuum chamber tobe used to execute a specific type of processing on the work substrate,an evacuation ring disposed so as to surround the stage and having anevacuating passage formed therein and an evacuation mechanism thatevacuates the vacuum chamber via the evacuating passage, characterizedin that the evacuation ring includes a side wall portion formedsubstantially perpendicular to the surface of the stage on which thework substrate is placed and a bottom portion ranging inward from thelower end of the side wall portion and in that the evacuating passage isformed at least at the side wall portion, is provided.

The side wall portion of the evacuation ring is constituted with aninner cylindrical member and an outer cylindrical member disposedcoaxially to each other over a predetermined distance from each other,which should be positioned so as to offset an opening at the innercylindrical member and an opening at the outer cylindrical member fromeach other.

In this structure, the opening at the inner cylindrical member and theopening at the outer cylindrical member may be formed in alongitudinally elongated rectangular shape, and the inner cylindricalmember and the outer cylindrical member may each have a plurality ofsuch openings set along the circumferential direction over predeterminedintervals.

In addition, the evacuating passage may be formed with the openingformed at the inner cylindrical member, a clearance formed between theinner cylindrical member and the outer cylindrical member and theopening formed at the outer cylindrical member.

Also, the evacuating passage may be formed at the bottom portion of theevacuation ring in the plasma processing apparatus.

In another aspect of the present invention, the object described aboveis achieved by providing a plasma processing apparatus comprising avacuum chamber in which a work substrate is placed, a stage disposedwithin the vacuum chamber on which the work substrate is placed, aplasma generating mechanism that generates plasma inside the vacuumchamber to be used to execute a specific type of processing on the worksubstrate, an evacuation ring disposed so as to surround the stage andhaving an evacuating passage formed therein and an evacuation mechanismthat evacuates the vacuum chamber from the bottom of the evacuation ringvia the evacuating passage, characterized in that the evacuation ringincludes a first member having a first opening and a second memberdisposed over a distance with a clearance formed between the firstmember and the second member and having a second opening formed at aposition offset from the first opening, in that the evacuating passageis formed to extend from the first opening into the clearance and passthrough the clearance to be led out from the second opening and in thatthe plasma is trapped inside the clearance.

The present invention achieved in an embodiment is now explained indetail in reference to drawings. FIG. 8 is a schematic illustration ofthe structure adopted in the embodiment achieved by adopting the presentinvention in a plane parallel plasma etching apparatus used to etchsemiconductor wafers. In FIG. 8, reference numeral 301 indicates acylindrical vacuum chamber constituted of, for instance, aluminum andhaving an internal space that can be closed off in an airtight state.

A stage 302 on which a semiconductor wafer W is placed is providedinside the vacuum chamber 301, and the stage 302 also functions as alower electrode. At the ceiling inside the vacuum chamber 301, a showerhead 303 constituting an upper electrode is disposed and a pair of plainparallel electrodes are constituted by the stage 302 and the shower head303.

A free space 304 in which the gas is diffused is formed at the showerhead 303 and numerous narrow holes 305 are formed on the lower siderelative to the free space 304 for gas diffusion. A specific type ofprocessing gas supplied from a processing gas supply system 306 isdiffused inside the free space 304 for gas diffusion, and the diffusedprocessing gas is then supplied in a shower directed toward thesemiconductor wafer W through the narrow holes 305. While the potentialat the shower head 303 is set to the ground level in the embodiment, ahigh-frequency source may be connected to the shower head 303 to applyhigh-frequency power both to the stage 302 and to the shower head 303,instead.

Two high-frequency sources 309 and 310 are connected to the stage 302via two matchers 307 and 308 respectively and, as a result,high-frequency power can be supplied to the stage 302 by superimposingthe high frequency power with one of the two different specificfrequencies (e.g., 100 MHz and 3.2 MHz) on the high frequency power withthe other frequency. It is to be noted that a single high-frequencysource may be used to supply high-frequency power to the stage 302 sothat high-frequency power with a single frequency is supplied to thestage 302, instead.

In addition, an electrostatic chuck 311 which electrostatically holdsthe semiconductor wafer W is provided at the surface of the stage 302 onwhich the semiconductor wafer W is placed. The electrostatic chuck 311adopts a structure achieved by disposing an electrostatic chuckelectrode 311 b inside an insulating layer 311 a, with a DC source 312connected to the electrostatic chuck electrode 311 b. A focus ring 313is provided at the upper surface of the stage 302 so as to surround thesemiconductor wafer W.

An evacuation port 314 is provided at the bottom of the vacuum chamber301, and an evacuation system 315 constituted of a vacuum pump and thelike is connected to the evacuation port 314.

An evacuation ring 316 formed in an annular shape is provided around thestage 302. As shown in FIG. 9, the evacuation ring 316 includes a sidewall portion 317 formed to range downward almost perpendicularly and abottom portion 318 ranging inward perpendicular to the bottom end of theside wall portion 317.

As shown in FIG. 10, the side wall portion 317 is constituted with aninner cylindrical member 319 and an outer cylindrical member 320disposed, coaxially to each other over a predetermined distance fromeach other. The inner cylindrical member 319 includes a plurality ofopenings 319 a formed in a vertically elongated rectangular shape andset over specific intervals along the circumferential direction toconstitute evacuating passages. In addition, as shown in FIGS. 10 and14, the outer cylindrical member 320, too, includes a plurality ofopenings 320 a formed in a vertically elongated rectangular shape toconstitute the evacuating passages. The openings 319 a and the openings320 a are disposed so that they are offset from each other by apredetermined extent (by the distance C in FIG. 11) along thecircumferential direction.

The evacuating passages are thus each formed so that the gas passesthrough the openings 319 a at the inner cylindrical member 319, thenpasses through a clearance 321 formed between the inner cylindricalmember 319 and the outer cylindrical member 320 and subsequently isdischarged through the openings 320 a at the outer cylindrical member320, as the arrows in FIG. 11 indicate.

The dimensions A to D in FIG. 11, i.e., the width A of the clearance321, the width B of the openings 319 a, the width C over which theopenings 319 a are offset relative to the corresponding openings 320 aand the thickness D of the inner cylindrical member 319 satisfy thefollowing conditions:C/A>1B>2AB/D>1

Namely, the evacuation ring 316 achieves a structure that traps plasmain the clearance 321, and in order to assure this, the width A of theclearance 321 is set relatively small, whereas the offset width C of theopenings 319 a and the openings 320 a is set large enough to trap theplasma.

In addition, the width B of the openings 319 a, which are not used totrap the plasma, is set to a large value to ensure a high enoughconductance level with a large opening area, and for the same reason,the thickness D of the inner cylindrical member 319 is set to a smallvalue. The thickness of the outer cylindrical member 320 and the widthof the openings 320 a, too, are set to similar values based upon thesame principle.

It is to be noted that FIG. 11 schematically illustrates the structureof the evacuation ring 316 and it does not indicate the actualdimensions accurately. In the actual application, the width B of theopenings 319 a is set greater than 2 mm, e.g., approximately severalmillimeters if, for instance, the width A of the clearance 321 is set to1 mm. The offset width C of the openings 319 a and the openings 320 aand the thickness D of the inner cylindrical member 319 are also set tovalues conforming to the conditions presented earlier and takingmachinability into consideration.

The length of the side wall portion 317 along the vertical direction,too, is set to a value that will allow the openings 319 a and theopenings 320 a to range over large enough areas and assures asatisfactory level of conductance.

By forming evacuating passages at the side wall portion 317 of theevacuation ring 316 and setting the length of the side wall portion 317along the vertical direction to a relatively large value, as describedabove, the openings are allowed to range over large enough areas andthus a satisfactory level of conductance is assured. In addition, sincethe diameter of the evacuation ring 316 does not need to be increasedeven though the openings range over great areas, the diameter of thevacuum chamber 301 itself does not need to increase, and thus, thefootprint of the apparatus remains unchanged.

Furthermore, by forming the evacuating passages at the side wall portion317 with the openings 319 a, the clearance 321 and the openings 320 a asdescribed above, the openings are allowed to range over large areas toassure a satisfactory level of conductance while assuring the requiredplasma leak preventing function, as well.

In other words, while electrons in the plasma are allowed to passthrough the openings 319 a ranging over large areas in the gas flowindicated by the arrows in FIG. 11, the outer cylindrical member 320 ispresent ahead as the electrons advance and thus, the likelihood of theelectrons further passing through the clearance 321 and being led out tothe outside through the openings 320 a is greatly lowered. Namely, sincethe plasma is highly unlikely to leak to the outside of the openings 320a, a satisfactory level of plasma leak preventing function can beassured even when the openings range over large areas to achieve a highlevel of conductance.

Moreover, numerous openings 318 a each constituted as a circular holeare formed at the bottom portion 318 of the evacuation ring 316 as well,and these openings 318 a, too, form evacuating passages in theembodiment. By forming evacuating passages at the bottom portion 318 inthis manner, the conductance can be further improved.

Instead of forming the evacuating passages at the bottom portion 318 ofthe evacuation ring 316 with openings such as circular holes asdescribed above, the evacuating passage at the bottom portion 318, mayadopt a structure identical to that of the evacuating passages at theside wall portion 317. However, since the bottom portion 318 is locatedat a considerable distance from the area in which plasma is formed, theevacuating passage at the bottom portion 318 can be formed with simplecircular holes or the like without having to consider the plasma leakpreventing function as a crucial factor. In addition, if a sufficientlyhigh level of conductance can be assured with the evacuating passagesformed at the side wall portion 317 alone, no evacuating passages needto be formed at the bottom portion 318.

The evacuation ring 316 described above may be formed by using anymaterial as long as it is electrically conductive and may be constitutedof, for instance, stainless steel or aluminum with an alumite film or asprayed coating deposited on the surface thereof. The evacuation ring316 constituted of a conductive material is electrically connected tothe ground potential.

As the vacuum chamber 301 is evacuated through the evacuation port 314via the evacuation ring 316 adopting the structure described above byutilizing the evacuation system 315, the atmosphere inside the vacuumchamber 301 achieves a predetermined degree of vacuum.

Furthermore, a magnetic field forming mechanism 322 is provided aroundthe vacuum chamber 301 so as to form a desired magnetic field in theprocessing space inside the vacuum chamber 301. The magnetic fieldforming mechanism 322 includes a rotating mechanism 323, and as themagnetic field forming mechanism 322 is rotated around the vacuumchamber 301, the magnetic field inside the vacuum chamber 301, too, isallowed to rotate.

Next, an etching process executed in the plasma etching apparatusstructured as described above is explained. First, a gate valve (notshown) at a transfer port (not shown) is opened, and a semiconductorwafer W carried into the vacuum chamber 301 with a transfer mechanism orthe like is set on the stage 302. The semiconductor wafer W placed onthe stage 302 is then electrostatically held onto the electrostaticchuck 311 by applying a predetermined level of a DC voltage to theelectrostatic chuck electrode 311 b of the electrostatic chuck 311 fromthe D.C. source 312.

Next, after moving the transfer mechanism out of the vacuum chamber 301,the gate valve is closed, the vacuum chamber 301 is evacuated with thevacuum pump or the like of the evacuation system 315, and then, after aspecific degree of vacuum is achieved inside the vacuum chamber 301, theprocessing gas to be used to execute a specific type of etching processis supplied from the processing gas supply system 306 into the vacuumchamber 301 via the free space 304 for gas diffusion and the narrowholes 305 at a flow rate of, for instance, 100 to 1000 sccm. Thus, thepressure inside the vacuum chamber 301 is sustained at, for instance,approximately 1.33 to 133 Pa (10 to 100 mTorr).

In this state, high-frequency power with specific frequencies (e.g., 100MHz and 3.2 MHz) is supplied to the stage 302 from the high-frequencysources 309 and 310.

As the high-frequency power is applied to the stage 302 as describedabove, a high-frequency electric field is formed in the processing spacebetween the shower head 303 and the stage 302. In addition, a specificmagnetic field is formed in the processing space by the magnetic fieldforming mechanism 322. Thus, a plasma with specific characteristics isgenerated from the processing gas supplied into the processing space,and a specific film on the semiconductor wafer W becomes etched with theplasma.

During this process, the high conductance at the evacuation ring 316makes it possible to evacuate the vacuum chamber with a high degree ofefficiency and, as a result, the atmosphere inside the vacuum chambereasily achieves a high degree of vacuum without having to employ alarge, high performance vacuum pump or the like. In addition, since aplasma leak can be prevented with a high degree of reliability at theevacuation ring 316, the desired etching process can be executed with ahigh level of accuracy with stable plasma.

After the specific etching process is executed, the supply of thehigh-frequency power from the high-frequency sources 309 and 310 isstopped, thereby ending the etching process, and then, the semiconductorwafer W is carried out of the vacuum chamber 301 by reversing theprocedure described earlier.

It is to be noted that while the present invention is adopted in aplasma etching apparatus that etches semiconductor wafers in theembodiment described above, the present invention is not limited to thisexample. For instance, it may be adopted in an apparatus that processessubstrates other than semiconductor wafers, or in an apparatus thatexecutes processing other than etching, e.g., a film formationprocessing apparatus that executes CVD or the like.

The plasma processing apparatus described above achieving a high levelof gas conductance capability supports a wide range of processes withoutnecessitating an increase in the production costs and enables the plasmaprocessing to be executed in a desirable manner with stable plasmaachieved through its high level of plasma leak preventing function.

(Another Example of a Plasma Processing Apparatus in Which the PresentInvention May Be Adopted)

Next, yet another example of the plasma processing apparatus in whichthe present invention may be adopted is explained. The present inventionis adopted in a plasma processing apparatus that executes plasmaprocessing on workpieces that may be glass substrates for flat displays(FPD) such as liquid crystal displays (LCD), i.e., FPD substrates suchas LCD substrates, as well as semiconductor wafers in this example. Morespecifically, an explanation is given in reference to the example on aplasma processing apparatus capable of implementing control so as todrive a member such as an electrode disposed within the plasmaprocessing apparatus to a desired position and its upper electrode unit.

In a plasma processing apparatus that executes plasma processing on aworkpiece such as a semiconductor wafer (hereafter simply referred to asa wafer) or an LCD substrate during various processes of semiconductordevices or LCD substrate production, follow-up control is normallyimplemented by utilizing a servomotor, a stepping motor or the like asan actuator to implement control so as to linearly drive a member suchas an a electrode disposed within the processing apparatus to a desiredposition.

In such a structure having a motor utilized as an actuator, a sturdystructural body is required to form a motive force communicatingmechanism constituted of a pulley, gears, a belt or a chain to be usedto convert the motor rotation to a linear motion, and thus, theprocessing apparatus itself is bound to be large in size. In addition,there is also a problem in that vibration and noise caused by therotational motion of the motor and the motive force communicatingmechanism adversely affect the results of the wafer processing.Furthermore, it requires a regular maintenance since the gears and thechain constituting the motive force communicating mechanism areconsumables.

While it is conceivable to utilize an actuator constituted of apneumatic actuator instead of a motor, the piping connection for apneumatic actuator is bound to be complex and there is also the concernthat an oil leak may cause contamination in the clean room. For thesereasons, a pneumatic actuator is not suitable for an application in aplasma processing apparatus.

As an alternative, a pneumatic actuator may be utilized as the actuator.A pneumatic actuator is advantageous in that there is no risk of an oilleak or contamination of the clean room. There is another advantage tothe pneumatic actuator in that it can be provided as a light weight,compact unit capable of achieving a high output. For these reasons,pneumatic actuators are used in plasma processing apparatusapplications, in a wafer cassette elevator mechanism (see, for instance,the Japanese Patent Laid-open Publication No. 2001-35897) and in a gateswitching mechanism (see, for instance, Japanese Patent Laid-openPublication No. 10-209245 (U.S. Pat. No. 6,113,734)) provided at thewafer transfer port in the processing chamber.

However, when a pneumatic actuator is used as the actuator to implementcontrol on the drive of a member disposed inside the plasma processingapparatus, the compressibility due to the material characteristicsinherent to air such as the viscosity and density, and the nonlinearityattributable to the communication delay compromise the controlperformance. In addition, the control performance is also affected byexternal factors such as the temperature. Thus, highly accuratepositional control, in particular, cannot easily be achieved with apneumatic actuator.

For this reason, a pneumatic actuator is primarily utilized in simpletasks such as a constant repetitive operation and is not deemed suitablefor drive control of, for instance, an electrode, in which highlyaccurate positional control must be achieved in the related art.

Accordingly, an object of the present invention, which has beencompleted by addressing the problems discussed above, is to provide aplasma processing apparatus and an upper electrode unit with whichhighly accurate positional control can be implemented by using apneumatic actuator.

In order to achieve the object described above, in a first aspect of thepresent invention, a plasma processing apparatus that executes plasmaprocessing on a workpiece with plasma generated by using an electrodedisposed inside a processing container, comprising a sliding supportmember that slidably supports the electrode with a slide mechanism sothat the electrode is allowed to slide freely along one direction, apneumatic cylinder having a rod disposed continuous with the slidingsupport member, a pneumatic circuit that drives the pneumatic cylinderand a means for control that implements positional control of theelectrode by controlling the pneumatic circuit, is provided.

A second aspect of the present invention achieves the object byproviding an upper electrode unit of a plasma processing apparatus thatexecutes plasma processing on a workpiece with plasma generated by usingan upper electrode disposed inside a processing container, comprisingthe upper electrode disposed inside the processing container, a slidingsupport member that slidably supports the upper electrode with a slidemechanism so as to allow the upper electrode to slide freely along thevertical direction, a pneumatic cylinder having a rod disposedcontinuous to the sliding support member, a pneumatic circuit thatdrives the pneumatic cylinder and a means for control that implementspositional control of the upper electrode by controlling the pneumaticcircuit.

According to the invention achieved in the first aspect and the secondaspect by adopting the structure described above, the sliding supportmember provided independently of the pneumatic cylinder slidablysupports the electrode so as to allow the electrode to slide freelyalong one direction (e.g., the vertical direction) and, as a result, anyload (external disturbance) that would otherwise be applied to thepneumatic cylinder along a direction other than the one direction iseliminated to engage the pneumatic cylinder in movement along onedirection exclusively. Consequently, highly accurate positional controlof the electrode is achieved with the pneumatic cylinder.

In addition, by providing the upper electrode, the drive mechanism ofthe upper electrode and the means for its control as an integrated unitas in the second aspect, the upper electrode unit can be installed intoan existing plasma processing apparatus with ease to achieve positionalcontrol for the upper electrode with a pneumatic cylinder.

The slide mechanism used in the first and second aspects may include arail disposed at the external circumference of the sliding supportmember along the direction in which electrode slides and a guide memberthat guides the rail along the sliding direction while supporting therail slidably and is fixed to the processing container. By adopting sucha slide mechanism, the electrode card be slidably supported through asimple structure. The guide member in this slide mechanism may be fixedto the processing container via a horizontal adjustment member of theelectrode. In such a case, a fine adjustment of the electrode along thehorizontal direction can be achieved readily by adjusting theinclination of the guide member with the horizontal adjustment member.

Also, the rod of the pneumatic cylinder used in the first and secondaspects may be disposed at an approximate center of the electrode. Thisstructure is effective in preventing decentering of a load applied tothe rod of the pneumatic cylinder and suppressing an occurrence ofmoment, and thus, even more accurate positional control of the electrodeis achieved.

Furthermore, the pneumatic circuit used in the first and second aspectsmay include a switching valve provided at a position between a pneumaticsource and the pneumatic cylinder, which enable drive of the rod of thepneumatic cylinder by switching the flow of compressed air supplied tothe pneumatic cylinder based upon a control signal provided by the meansfor control and a drive stop valve disposed at a position between theswitching valve and the pneumatic cylinder, which allows the rod of thepneumatic cylinder to stop and be held by cutting off the compressed airsupplied to the pneumatic cylinder based upon a stop signal provided bythe means for control. By adopting such a structure in the pneumaticcircuit, it becomes possible to control the position to which theelectrode moves and the direction along which the electrode moves withthe means for control, and thus, if an abnormality occurs in the plasmaprocessing apparatus, the movement of the electrode can be stopped andthe electrode can be held at the stop position.

In addition, a means for positional detection that detects the positionof the electrode by detecting the movement of the rod at the pneumaticcylinder used in the first and second aspects may be provided to allowthe means for control to implement the positional control of theelectrode based upon a deviation determined by subtracting the currentposition of the electrode detected with the means for positionaldetection from a target position set for the electrode. In such a case,the target position may be set over a plurality of stages leading to theposition to which the electrode is to be ultimately moved, so as todrive the electrode gradually. By driving the electrode gradually inthis manner, the occurrence of abrupt drive and vibration caused bymaterial characteristics inherent to the air used to drive the pneumaticcylinder such as the viscosity and the density can be minimized. Thus,while the upper electrode is driven with the pneumatic cylinder,problems such as attracting particles and the like in the processingcontainer, for instance, can be prevented.

It is to be noted that the electrode referred to in the description ofthe first aspect is one of a pair of electrodes disposed parallel toeach other inside the processing container, and the workpiece may beplaced on the other electrode.

The following is a detailed explanation of a preferred embodiment of thepresent invention, given in reference to attached drawings. It is to benoted that in the specification and the drawings, the same referencenumerals are assigned to components having substantially identicalfunctions and structural features to preclude the necessity for arepeated explanation thereof.

FIGS. 12 and 13 schematically illustrates the structure adopted in aplane parallel plasma processing apparatus 400, which is a typicalexample of the plasma processing apparatus achieved in the embodiment ofthe present invention. FIG. 12 shows the upper electrode set at theretracted position, whereas FIG. 13 shows the upper electrode set at theprocessing position. FIG. 14 schematically illustrates the mechanismused to drive the upper electrode shown in FIGS. 12 and 13 to facilitatean explanation of its functions, with FIG. 14A showing a state in whichthe upper electrode is set at the retracted position and FIG. 14Bshowing a state in which the upper electrode is set at the processingposition.

The plasma processing apparatus 400 achieved in the embodiment includesa cylindrical chamber (processing container) 402 constituted of aluminumwith a surface thereof having undergone anodization (alumiteprocessing), and the chamber 402 is grounded.

A susceptor stage 404 formed in a substantially columnar shape, on whicha workpiece such as a semiconductor wafer (a hereafter simply referredto as a “wafer”) W is placed is provided at the bottom inside thechamber 402 via an insulating plate 403 constituted of ceramic or thelike. A susceptor 405 constituting a lower electrode is set on thesusceptor stage 404. A high pass filter (HPF) 106 is connected to thesusceptor 405.

Inside the susceptor stage 404, a temperature adjustment medium chamber407 is formed. A temperature adjustment medium which is guided into thetemperature adjustment medium chamber 407 via a supply pipe 408 is madeto circulate within the temperature adjustment medium chamber 407 andthen is discharged through a discharge pipe 409. With the temperatureadjustment medium circulating in this manner, the temperature of thesusceptor 405 is adjusted to a desired level.

An electrostatic chuck 411 assuming a shape substantially identical tothat of the wafer W is disposed on the central portion of the susceptor405 on the upper side, which is formed as a projecting disk. Theelectrostatic chuck 411 is achieved by setting an electrode 412 betweeninsulating members. A DC voltage at, for instance, 1.5 kV is applied tothe electrostatic chuck 411 from a DC electrode 413 connected to theelectrode 412. As a result, the wafer W becomes electrostatically heldonto the electrostatic chuck 411.

At the insulating plate 403, the susceptor stage 404, the susceptor 405and the electrostatic chuck 411, a gas passage 414 through which a heattransfer medium (e.g., a back side gas such as an He gas) is supplied tothe rear surface of the workpiece i.e., the wafer W, is formed. The heatis transferred between the susceptor 405 and the wafer W via the heattransfer medium, thereby sustaining the temperature of the wafer W at apredetermined level.

An annular focus ring 415 is disposed at the edge of the susceptor 405at its upper end so as to surround the wafer W placed on theelectrostatic chuck 411. The focus ring 415 is constituted of aninsulating material such as ceramic or quartz, or an electricallyconductive material. The presence of the focus ring 415 improves theetching uniformity.

An evacuation pipe 431 is connected at the bottom of the chamber 402,and an evacuation device 435 is connected to the evacuation pipe 431.The evacuation device 435, which includes a vacuum pump such as a turbomolecular pump, adjusts the pressure of the atmosphere inside thechamber 402 to a predetermined lower level (e.g., 0.67 Pa or lower). Inaddition, a gate valve 432 is provided at the side wall of the chamber402. As the gate valve 432 opens, a transfer of the wafer W into/out ofthe chamber 402 is enabled. It is to be noted that the wafer W istransferred with, for instance, a transfer arm.

In addition, an upper electrode 420 is disposed above the susceptor 405to run parallel to the susceptor 405 and to face opposite the susceptor405. The upper electrode 420 can be driven along one direction, e.g.,the vertical direction, by an upper electrode drive mechanism 500. Thus,the distance between the susceptor 405 and the upper electrode 420 canbe adjusted. It is to be noted that the upper electrode drive mechanism500 is to be described in detail later.

The upper electrode 420 is supported at the inner wall of the ceiling ofthe chamber 402 via a bellows 422. The bellows 422 is mounted at theinner wall at the ceiling of the chamber 402 with a fastening means suchas a bolt via an annular upper flange 422 a and is also attached to theupper surface of the upper electrode 420 with a fastening means such asa bolt via an down flange 422 b.

The upper electrode 420 includes an electrode plate 424 constituting asurface facing opposite the susceptor 405 and having numerous outletholes 423 and an electrode support member 425 that supports theelectrode plate 424. The electrode plate 424 is constituted of, forinstance, quartz, whereas the electrode support member 425 isconstituted of an electrically conductive material such as aluminum witha surface thereof having undergone alumite processing.

A gas supply port 426 is provided at the electrode support member 425 ofthe upper electrode 420. A gas supply pipe 427 is connected to the gassupply port 426. In addition, a processing gas supply source 430 isconnected to the gas supply pipe 427 via a valve 428 and a mass flowcontroller 429.

An etching gas, for instance, to be used to execute plasma etching issupplied from the processing gas supply source 430. It is to be notedthat while FIG. 12 shows a single processing gas supply systemcomprising the gas supply pipe 427, the valve 428, the mass flowcontroller 429, the processing gas supply source 430 and the like, theplasma processing apparatus 400 includes a plurality of processing gassupply systems in reality. Namely, CHF8, Ar and He, for instance, toconstitute to the processing gas, the flow rates of which are controlledindependently of one another, are individually supplied into the chamber402.

A first high-frequency source 440 is connected to the upper electrode420, with a first matcher 441 inserted at the power supply line. Inaddition, a low pass filter (LPF) 442 is connected to the upperelectrode 420. The first high-frequency source 440 is capable ofoutputting power at a frequency in the range of 50 to 150 MHz. As thepower at such a high-frequency is applied to the upper electrode 420,high-density plasma can be formed in a desired state of dissociationinside the chamber 402 and plasma processing can be executed at a lowerpressure compared to the related art. Ideally, the frequency of thepower output from the first high-frequency source 440 should be 50 to 80MHz, and typically, it is adjusted to 60 MHz as shown in the figure orto a value close to 60 MHz.

A second high-frequency source 450 is connected to the susceptor 405constituting the lower electrode, with a second matcher 451 inserted atthe power supply line. The second high-frequency source 450 is capableof outputting power at a frequency in the range of several hundred kHzto several tens of MHz. As the power at a frequency in this range isapplied to the susceptor 405, a desired ionization effect can beachieved without damaging the workpiece, i.e., the wafer W. Typically,the frequency of the power output from the second high-frequency source450 is adjusted to 2 MHz, as shown in the figure, or to 13.56 MHz.

Next, the upper electrode drive mechanism 500 is explained in detail.The upper electrode drive mechanism 500 includes a substantiallycylindrical sliding support member 504 that slidably supports the upperelectrode 420 so as to allow the upper electrode 420 to slide relativeto the chamber 402. The sliding support member 504 is mounted at anapproximate center of the top surface of the upper electrode 420 with abolt or the like.

The sliding support member 504 is disposed so that it is allowed tofreely enter and withdraw from a hole 402 a formed at an approximatecenter of the upper wall of the chamber 402. More specifically, theexternal circumferential surface of the sliding support member 504 isslidably supported at the edge of the hole 402 a at the chamber 402 viaa slide mechanism 510.

The slide mechanism 510 includes a guide member 516 retained at avertical portion of a retaining member 514 having an L-shaped sectionand disposed, for instance, at the top of the chamber 402 and a railportion 512 slidably supported by the guide member 516 and formed toextend along one direction (the vertical direction in the embodiment) atthe external circumferential surface of the sliding support member 504.

The retaining member 514, which securely retains the guide member 516 ofthe slide mechanism 510 includes a horizontal portion fixed to the topof the chamber 402 via an annular horizontal adjustment plate 518. Thehorizontal adjustment plate 518 is used to adjust the horizontalposition of the upper electrode 420. The horizontal adjustment plate 518may be secured onto the chamber 402 with a plurality of bolts or thelike set over uniform intervals along the circumferential direction soas to adjust the extent of inclination of the horizontal adjustmentplate 518 along the horizontal direction in correspondence to theextents to which the individual bolts protrude. As the inclination ofthe guide member 516 at the slide mechanism 510 along the verticaldirection is adjusted by adjusting the inclination of the horizontaladjustment plate 518 along the horizontal direction, the inclination ofthe upper electrode 420 supported via the guide member 516 is adjustedalong the horizontal direction. As a result, it is possible to retainthe upper electrode 420 at the correct horizontal position at all timesthrough a simple operation.

A pneumatic cylinder 520 used to drive the upper electrode 420 ismounted on the upper side of the chamber 402 via a barrel body 501.Namely, the lower end of the barrel body 501 is mounted by assuring airtightness with a bolt or the like so as to cover the hole 402 a at thechamber 402 and the upper end of the barrel body 501 is mounted byassuring air tightness at the lower end of the pneumatic cylinder 520.

The pneumatic cylinder 520 includes a rod 502 that can be driven alongone direction, and the lower end of the rod 502 is disposed continuousto an approximate center area on the upper side of the sliding supportmember 504 with a bolt or the like. Thus, as the rod 502 of thepneumatic cylinder 520 is driven, the upper electrode 420, too, isdriven by the sliding support member 504 along the slide mechanism inone direction. As the inner space of the rod 502 assuming a cylindricalshape comes into communication with a central hole formed at anapproximate center of the sliding support member 504, the rod is set ina state of communication with the atmosphere. Thus, the power supplyline from the matcher 441 or the like can be connected to the upperelectrode 420 through the inner space of the rod 502 via the centralhole at the sliding support member 504.

In addition, a means for positional detection such as a linear encoder505 that detects the position of the upper electrode 420 is provided tothe side of the pneumatic cylinder 520. An upper end member 507 havingan extension 507 a extending sideways from the rod 502 is provided atthe upper end of the rod 502 of the pneumatic cylinder 520, and adetection portion 505 a of the linear encoder 505 is in contact with theextension 507 a of the upper end member 507. Since the upper end member507 interlocks with the Movement of the upper electrode 420, theposition of the upper electrode 420 can be detected with the linearencoder 505.

The pneumatic cylinder 520 is constituted by enclosing a tubularcylinder main body 522 with an upper support plate 524 and a lowersupport plate 526. An annular partitioning member 508 that partitionsthe inner space of the pneumatic cylinder 520 into an upper space 532and a lower space 534 is disposed on the external circumferentialsurface of the rod 502.

As shown in FIG. 14, compressed air is supplied into the upper space 532of the pneumatic cylinder 520 from an upper port 536 at the uppersupport plate 524. Compressed air is also supplied into the lower space534 of the pneumatic cylinder 520 from a lower port 538 at the lowersupport plate 526. By controlling the quantities of air supplied intothe upper space 532 and the lower space 534 from the upper port 536 andthe lower port 538 respectively, the drive of the rod 502 along the onedirection (the vertical direction in this example) can be controlled.The quantities of air supplied into the pneumatic cylinder 520 arecontrolled at a pneumatic circuit 610 provided near the pneumaticcylinder 520.

Next, a means for drive control 600 provided in the plasma processingapparatus in the embodiment as part of the upper electrode drivemechanism 500 is explained. FIG. 15 is a circuit diagram of the meansfor drive control 600 provided as part of the upper electrode drivemechanism 500 and FIG. 16 is a block diagram of the pneumatic circuit610.

As shown in FIG. 15, the means for drive control 600 is constituted withthe pneumatic circuit 610 and a means for control 700 that controls thepneumatic circuit 610. The means for control 700 includes a CPU (centralprocessing unit) 720 constituting the main body of the means for control700, an interface 740 that exchanges various signals with the externalapparatuses, an interlock circuit 760 used to execute a self diagnosisof the pneumatic circuit 610 and the like. The interface 740 exchangescontrol signals with a control device (not shown) that controls theplasma processing apparatus 400 and also receives sensor signals fromvarious sensors. The signals input to the interface 740 include an upperelectrode drive control signal containing target position informationused to drive the upper electrode 420 to a specific target position andthe like, a gate valve control signal used to control the gate valve andsensor signals from the various sensors. In addition, the signals outputfrom the interface 740 include an upper electrode position stable signalindicating whether or not the position of the upper electrode 420 hasstabilized and whether or not the movement of the upper electrode 420has been completed and a wafer transfer signal indicating whether or notthe upper electrode 420 is set at a position out of the transfer path ofthe transfer arm transferring a wafer and thus the wafer can be safelytransferred into the chamber 402.

The sensor signals include a signal from an origin point sensor thatdetects whether or not the upper electrode 420 is positioned at theorigin point. The origin point as referred to in this context is theorigin point of the means for upper electrode positional detection suchas the linear encoder 505. In more specific terms, the origin pointsensor may be constituted with, for instance, a contact sensor or anoptical sensor. In such a case, the origin point sensor may be disposedon the inner side of the upper wall constituting the barrel body 501 onthe chamber 402, and the position at which the origin point sensordetects the upper end of the sliding support member 504, i.e., theuppermost position of the upper electrode 420 ₀ may be set as the originpoint. Another sensor signal input to the interface 740 is a transferverification position sensor signal inquiring whether or not the upperelectrode 420 is set at a position that allows a wafer transfer. Inresponse to the transfer verification position sensor signal input tothe interface 740, the CPU 720 detects whether or not the upperelectrode 420 is currently set at a position, i.e., a retractedposition, at which the upper electrode 420 is out of the way of thetransfer arm transferring the wafer based upon the detection signalprovided by the linear encoder 505 and outputs a wafer transfer signalvia the interface 740.

The interlock circuit 760, to which a signal from a switch 620 thatdetects whether or not compressed air is output from a pneumatic source605 in the pneumatic circuit 610 to drive the upper electrode 420 isinput, outputs a drive enabled signal to the pneumatic circuit 610 ifcompressed air is output from the pneumatic source 605, i.e., if thesignal from the switch 620 indicates an ON state. If, on the other hand,no compressed air is output from the pneumatic source 605, i.e., if thesignal from the switch 620 indicates an OFF state, it stops the outputof the drive enabled signal to the pneumatic circuit 610.

In addition, the interlock circuit 760 stops the output of the driveenabled signal to the pneumatic circuit 610 if an external interlocksignal is input even when the signal from the switch 620 indicates an ONstate. The interlock signal is input from the control device (not shown)to the means for control 700 when, for instance, an abnormalitynecessitating the drive of the upper electrode 420 to be stopped occursin the plasma processing apparatus 400.

The CPU 720 controls the pneumatic circuit 610 based upon the signalsfrom the interface 740. It controls the movement of the upper electrode420 so as to position the upper electrode 420 at the target positionthrough feedback control achieved by implementing PID control (controlexecuted by combining a proportional operation, a differential operationand an integration operation) as indicated in the block diagram in FIG.16, for instance. In the block diagram shown in FIG. 16, Ref (s) is thetarget position for the upper electrode 420 and Y(s) is the currentposition. G(s) is the transfer function, and K_(P), K_(I), K_(D), K_(A)and K_(V) respectively indicate the proportional gain, the integralgain, the differential gain, the acceleration feedback gain and thevelocity feedback gain.

More specifically, the deviation is determined by subtracting thecurrent position from the target position set for the upper electrode420, and PID control is implemented based upon an output (which can beadjusted in correspondence to the integral gain K_(I)) in proportion tothe time integral of the deviation and used to correct the steady statedeviation, an output (which can be adjusted in correspondence to thedifferential gain K_(D)) in proportion to the time-varying change in thedeviation and used to minimize the change rate and an output (which canbe adjusted in correspondence to the proportional gain K_(P)) inproportion to the deviation. Namely, in this PID control, a function ofpredicting the movement which is in proportion to the current deviation(a proportional operation), a function of eliminating the offset byholding the integral of the previous deviation (an integrationoperation) and a function of predicting future movement (a differentialoperation) are incorporated.

In addition, the pneumatic circuit 610 is controlled in the embodimentthrough the acceleration feedback control, implemented based uponoutputs from pressure sensors (not shown) disposed at the ports 536 and538 of the pneumatic cylinder 520 in order to control the externaldisturbance, as shown in FIG. 16, and the velocity feedback controlimplemented based upon the output of the linear encoder 505 taken intothe means for control 700, as shown in FIG. 15.

The positional control of the upper electrode 420 may be achieved bysetting the target position over a plurality of stages preceding theultimate position to which the upper electrode 420 is to be moved and bydriving the upper electrode 420 gradually. In this case, abrupt drive orabrupt vibration attributable to material properties such as theviscosity and the density of the air used to drive the pneumaticcylinder can be minimized. As a result, problems of attracting particlesinside the chamber 402 and the like while driving the upper electrodewith a pneumatic cylinder do not occur.

A structural example that may be adopted in the pneumatic circuit 610 isnow explained. FIG. 17 is a circuit diagram of a structure that may beadopted in the pneumatic circuit 610. FIGS. 18 and 19 are functionaldiagrams illustrating the operation of the pneumatic circuit 610. Thepneumatic circuit 610 is in a neutral state in FIG. 17, is engaged inthe drive control of the upper electrode 420 in FIG. 18 and is in astate of emergency stop in FIG. 19.

As shown in FIGS. 15 and 17, the pneumatic circuit 610 includes a 5-portelectromagnetic valve 630 constituting a switching valve capable ofswitching the flow path to a neutral state or a drive control state inresponse to a valve control signal provided by the CPU 720. A 5-portswitching valve 640 is disposed in a pipeline extending from the 5-portelectromagnetic valve 630 and communicating with the upper port 536 ofthe pneumatic cylinder 520, and a 5-port switching valve 650 is disposedin the pipeline extending from the 5-port electromagnetic valve 630 andcommunicating with the lower port 538 of the pneumatic cylinder 520.These 5-port switching valves 640 and 650, each used as a drive stopvalve when effecting an emergency stop of the pneumatic cylinder 520,can be controlled with a 3-port electromagnetic valve 660.

Now, the specific relationship with which the individual valves areconnected with each other is explained. The pneumatic source 605 isconnected to a p-port of the 5-port electromagnetic valve 630, and ana-port of the 5-port electromagnetic valve 630 is connected to a p-portof the 5-port switching valve 640. In addition, a b-port of the 5-portelectromagnetic valve 630 is connected to a p-port of the 5-portswitching valve 650. A c-port and a d-port of the 5-port electromagneticvalve 630 are used as discharge ports.

With the 5-port electromagnetic valve 630, the flow path can be switchedto an N state, an L state or an R state. A force applying member such asa spring is disposed on each side of the 5-port electromagnetic valve630, and a force is applied to the 5-port electromagnetic valve 630 toset it in the N state unless power is supplied in response to a valvecontrol signal provided by the means for control 700. Then, if positivepower is supplied in response to the valve control signal, for instance,the 5-port electromagnetic valve 630 is set in the L state against theforce applied by the force applying members, whereas if negative poweris applied in response to the valve control signal, the 5-portelectromagnetic valve 630 is set in the R state against the forceapplied by the force applying members. When the 5-port electromagneticvalve 630 is in the N state, each port at the 5-port electromagneticvalve 630 is in a cut-off state. When the 5-port electromagnetic valve630 is in the L state, its p-port and a-port are connected with eachother and its d-port and b-port are connected with each other, whereaswhen the 5-port electromagnetic valve 630 is in the R state, its p-portand b-port are connected with each other and its c-port and a-port areconnected with each other.

The upper port 536 of the pneumatic cylinder 520 is connected to ana-port of the 5-port switching valve 640 whereas the lower port 538 isconnected to an a-port of the 5-port switching valve 650. With both the5-port switching valve 640 and the 5-port switching valve 650, the flowpath can be switched to either the N state or the L state. At each ofthe 5-port switching valves 640 and 650, a force applying members suchas a spring is provided on one side thereof to apply a force to the5-port switching valve to set it in the N state unless compressed air issupplied through the 3-port electromagnetic valve 660. As compressed airis supplied through the 3-port electromagnetic valve 660, the 5-portswitching valves enter the L state against the force applied by theforce applying members. At each of the 5-port switching valves 640 and650, the p-port and a b-port are connected with each other and a c-portand the a-port are connected with each other in the N state, and thep-port and the a-port are connected with each other and the d-port andthe b-port are connected with each other in the L state.

The pneumatic source 605 is connected to a p-port of the 3-portelectromagnetic valve 660, and a b-port and an a-port at the 3-portelectromagnetic valve 660 are connected with each other. It is to benoted that the b-port at the 3-port electromagnetic valve 660 is used asa discharge port. As shown in FIG. 15, the flow path is switched toeither the N state or the L state at the 3-port electromagnetic valve660 based upon the drive enabled signal provided by the interlockcircuit 760. A force applying member such as a spring is provided on oneside of the 3-port electromagnetic valve 660 and a force is applied toset the 3-port electromagnetic valve 660 in the N state unless power issupplied in response to the drive enabled signal provided by the meansfor control 700. Then, as the drive enabled signal is output, it entersthe L state against the force applied by the force applying member. Atthe 3-port electromagnetic valve 660, the p-port is cut off and theb-port and the a-port are connected with each other in the N state,whereas the p-port and the a-port are connected with each other and theb-port is cut off in the L state.

When the switch 620 of the pneumatic source 605 is in an OFF state, asshown in FIG. 17, the output of the drive enabled signal from theinterlock circuit 760 is stopped and thus, the flow path at the 3-portelectromagnetic valve 660 is in the N state and the flow path at the5-port electromagnetic valve 630, too, is in the N state in thepneumatic circuit 610 adopting the structure described above. In thisneutral state, the ports 536 and 538 at the pneumatic cylinder 520 arecut off from the pneumatic source 605 by the 5-port electromagneticvalve 630, and, as a result, the upper electrode 420 is held in astopped state.

As the switch 620 of the pneumatic source 605 is turned on, the driveenabled signal is output from the interlock circuit 760, thereby settingthe flow path at the 3-port electromagnetic valve 660 in the L state. Asa result, the flow path at the 5-port switching valves 640 and 650 eachenter the L state. Consequently, drive of the upper electrode 420 isenabled with the compressed air supplied to the pneumatic cylinder 520by switching the flow path at the 5-port electromagnetic valve 630.

When the upper electrode 420 is to move downward, for instance, fromthis state, the flow path at the 5-port electromagnetic valve 630 is setin the L state, as shown in FIG. 18. In response, the compressed airfrom the pneumatic source 605 is guided in through the upper port 536 atthe pneumatic cylinder 520 and is discharged through the lower port 538,causing the sliding support member 504 to move downward and ultimatelycausing the upper electrode 420 to move downward.

When the upper electrode 420 is to move upward, for instance, from theneutral state shown in FIG. 17, the flow path at the 5-portelectromagnetic valve 630 is set in the N state unlike in the operationshown in FIG. 18. As the stop signal from the interlock circuit 760enters the OFF state, the flow path at the 3-port electromagnetic valve660 is set in the L state under these circumstances as well. As aresult, the flow paths at both the 5-port switching valve 640 and the5-port switching valve 650 are set in the L state. In response, thecompressed air from the pneumatic source 605 is guided in through thelower port 538 at the pneumatic cylinder 520 and then discharged throughthe upper port 536, causing the sliding support member 504 to moveupward and ultimately causing the upper electrode 420 to move upward.

FIG. 19 shows the state of the pneumatic circuit 610 when an emergencystop is applied while driving the upper electrode. As the stop signalfrom the interlock circuit 760 is turned on, the flow path at the 3-portelectromagnetic valve 660 enters the N state. As a result, the flowpaths at the 5-port switching valves 640 and 650 both enter the N state.In response, the compressed air from the pneumatic source 605 is guidedthrough the lower port 538 at the pneumatic cylinder 520, and thecompressed air from the pneumatic source 605 is cut off from both theupper part 536 and the lower port 538 at the pneumatic cylinder 520,thereby stopping the sliding support member 504 and stopping the upperelectrode 420.

FIGS. 20 and 21 present the results of tests conducted by implementingthe specific control shown in FIG. 16 with the pneumatic circuit 610achieved in the embodiment as described above with the target positionset over a plurality of stages preceding the ultimate position to whichthe upper electrode 420 was to move. FIG. 20 is a graph of therelationship between the position of the upper electrode 420 and thetime observed by gradually driving the upper electrode 420 upward,whereas FIG. 21 is a graph of the relationship between the position ofthe upper electrode 420 and the time, observed by gradually driving theupper electrode 420 downward. FIGS. 20 and 21 indicate that stable andaccurate follow-up control was achieved to drive the upper electrode 420upward or downward to set the target position.

Various indices measured based upon these test results, which includeapproximately ±0.15 mm representing the accuracy with which the upperelectrode was stopped and approximately 60 mm/sec representing theoperating speed, indicate that the structure adopted in the embodimentis highly viable in practical application. In other words, highlyaccurate positional control is enabled by employing the plasmaprocessing apparatus 400

In the plasma processing apparatus in the embodiment described in detailabove, the sliding support member 504 is provided independently of thepneumatic cylinder 520 to slidably support the upper electrode 420 alongone direction (e.g., the vertical direction), and thus, any load(external disturbance) that would be applied to the pneumatic cylinder520 along a direction other than the one direction is eliminated toallow the pneumatic cylinder 520 to move only along the one direction.Consequently, the positional control for the upper electrode 420 can beimplemented with a high degree of accuracy with the pneumatic cylinder520.

The rod 502 at the pneumatic cylinder 520 is disposed at an approximatecenter of the upper electrode 420 to prevent decentering of the loadapplied to the rod 502 at the pneumatic cylinder 520 and the occurrenceof a moment and, as a result, the position of the electrode can becontrolled with an even higher degree of accuracy.

It is to be noted that while the upper electrode 420 is driven by usingthe pneumatic cylinder 520 in the embodiment described above, the lowerelectrode may instead be slidably supported and be driven with thepneumatic cylinder 520. However, at the lower electrode on which theworkpiece such as a wafer or a liquid crystal substrate is placed,various additional mechanisms including a workpiece holding mechanism, aworkpiece back side gas mechanism and an electrode temperatureadjustment mechanism must be mounted, whereas the upper electrode doesnot need such additional mechanisms. For this reason, a higher degree ofpositional control accuracy can be achieved for the upper electrode 420by driving the upper electrode 420 with the pneumatic cylinder and thusminimizing the load applied to the rod 502 at the pneumatic cylinder520.

In addition, the components such as the upper electrode 420, the upperelectrode drive mechanism 500 for the upper electrode 420, the pneumaticcircuit 610 and the means for control 700 may be provided as anintegrated upper electrode unit, as shown in FIG. 14, to facilitatepositional control to be implemented with a pneumatic cylinder on anupper electrode 420 in an existing plasma processing apparatus simply byinstalling the upper electrode unit.

In conjunction with the plasma processing apparatus and the upperelectrode unit described above, highly accurate positional control canbe achieved with a pneumatic cylinder functioning as a pneumaticactuator by minimizing the load applied to the pneumatic cylinder.

It is to be noted that while an explanation is given above in referenceto the embodiment on an example in which the present invention isadopted in a plasma etching apparatus, the present invention may insteadbe adopted in a different type of processing apparatus such as a filmforming apparatus or an ashing apparatus. In addition, while theworkpiece processed in the embodiment described above is a semiconductorwafer, the present invention is not limited to this example, and thepresent invention may be adopted to process a workpiece such as a glasssubstrate for a flat display (FPD) in a liquid crystal display (LCD)device, i.e., an FPD substrate which may be an LCD substrate.

1. A plasma processing apparatus that executes plasma processing on aworkpiece disposed inside a processing container, the plasma processingapparatus comprising: an electrode disposed inside the processingcontainer; a sliding support member that slidably supports the electrodewith a slide mechanism so as to allow the electrode to slide freelyalong any direction; a pneumatic cylinder having a rod disposedcontinuous to the sliding support member; a pneumatic circuit thatdrives the pneumatic cylinder; and a means for control that implementspositional control of the electrode by controlling the pneumaticcircuit, wherein the slide mechanism comprises: a rail disposed at theexternal circumference of the sliding support member along the directionin which the electrode slides; and a guide member that guides the railalong the sliding direction while supporting the rail slidably and isfixed to the processing container.
 2. The plasma processing apparatusaccording to claim 1, wherein: the guide member is fixed to theprocessing container via a horizontal adjustment member of theelectrode.
 3. The plasma processing apparatus according to claim 1,wherein: the rod of the pneumatic cylinder is disposed at an approximatecenter of the electrode.
 4. The plasma processing apparatus according toclaim 1, wherein: the pneumatic circuit includes; a switching valveprovided at a position between a pneumatic source and the pneumaticcylinder, which enable drive of the rod of the pneumatic cylinder byswitching the flow of compressed air supplied to the pneumatic cylinderbased upon a control signal provided by the means for control; and adrive stop valve disposed at a position between the switching valve andthe pneumatic cylinder, which allows the rod of the pneumatic cylinderto stop and be held by cutting off the compressed air supplied to thepneumatic cylinder based upon a stop signal provided by the means forcontrol.
 5. The plasma processing apparatus according to claim 1,further comprising: a means for positional detection that detects theposition of the electrode by detecting the movement of the rod at thepneumatic cylinder; and wherein: the means for control implements thepositional control of the electrode based upon a deviation determined bysubtracting the current position of the electrode detected with themeans for positional detection from a target position set for theelectrode.
 6. The plasma processing apparatus according to claim 5,wherein: the means for control sets the target position over a pluralityof stages leading to the position to which the electrode is to beultimately moved, so as to drive the electrode gradually.
 7. The plasmaprocessing apparatus according to claim 1, wherein: the electrode is oneof a pair of electrodes disposed parallel to each other inside theprocessing container; and the workpiece is placed on the otherelectrode.
 8. An upper electrode unit of a plasma processing apparatusthat executes plasma processing on a workpiece disposed inside aprocessing container, the upper electrode unit comprising: an upperelectrode disposed inside the processing container; a sliding supportmember that slidably supports the upper electrode with a slide mechanismso as to allow the upper electrode to slide freely along any direction;a pneumatic cylinder having a rod disposed continuous to the slidingsupport member; a pneumatic circuit that drives the pneumatic cylinder;and a means for control that implements positional control of the upperelectrode by controlling the pneumatic circuit, wherein the slidemechanism comprises: a rail disposed at the external circumference ofthe sliding support member along the direction in which upper electrodeslides; and a guide member that guides the rail along the slidingdirection while supporting the rail slidably and is fixed to theprocessing container.
 9. The upper electrode unit according to claim 8,wherein: the guide member is fixed to the processing container via ahorizontal adjustment member of the upper electrode.
 10. The upperelectrode unit according to claim 8, wherein: the rod of the pneumaticcylinder is disposed at an approximate center of the upper electrode.11. The upper electrode unit according to claim 8, wherein: thepneumatic circuit includes; a switching valve provided at a positionbetween a pneumatic source and the pneumatic cylinder, which enabledrive of the rod of the pneumatic cylinder by switching the flow ofcompressed air supplied to the pneumatic cylinder based upon a controlsignal provided by the means for control; and a drive stop valvedisposed at a position between the switching valve and the pneumaticcylinder, which allows the rod of the pneumatic cylinder to stop and beheld by cutting off the compressed air supplied to the pneumaticcylinder based upon a stop signal provided by the means for control. 12.The upper electrode unit according to claim 8, further comprising: ameans for positional detection that detects the position of the upperelectrode by detecting the movement of the rod at the pneumaticcylinder; and wherein: the means for control implements the positionalcontrol of the upper electrode based upon a deviation determined bysubtracting the current position of the upper electrode detected withthe means for positional detection from a target position set for theupper electrode.
 13. The upper electrode unit according to claim 12,wherein: the means for control sets the target position over a pluralityof stages leading to the position to which the upper electrode is to beultimately moved, so as to drive the upper electrode gradually.